Community Research and Development Information Service - CORDIS

Ferritic rolling of ULC steels

Ferritic rolling at low temperature (less than 800 C) in the finishing mill appears to be an economical way to produce a thin and extra soft hot strip.
The operating costs can be lowerwhen compared to the conventional austenitic practice.

The laboratory studies and the industrial trials on the finishing mill show that the final mechanical properties are dependent on the process parameters as well as on the steel chemistry. A distinction is made between:
the thin hot strip (2.5 mm to 2 mm) with a complete recrystallized ferritic microstructure for direct applications (in ELC steels ferritic rolling is associated with a coiling temperature between 600 and 650 C to produce a very soft nonaging steel grade, with a remarkable ductility and in ULC titanium steels, higher coiling temperatures are needed to develop recrystallization);
the same very soft strips for cold rolling and annealing, to reduce cold rolling loads and torques or to enlarge the rolling limits (in ELC steels, a CQ grade is easily produced and in ULC-titanium steels, the DDQ grade can be obtained;
the thin (less than 1.5 mm) hot strip with a strained microstructure for direct annealing, in a galvanizing line for example.

Lowering both rolling and coiling temperatures causes the development of a strained ferritic microstructure. Direct recrystallization allows CQ (ELC steels) or DQ (ULC-Titanium steels) grades to be produced. Best properties are obtained when hot rolling is performed on lubricated rolls.

Reported by

Centre de Recherches Metallurgiques
11 rue Ernest Solvay
4000 Liege
Belgium
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